The present invention relates to a passenger protection device installed in a vehicle, and more particularly relates to a technique for configuring a passenger protection device so as to implement thorough passenger protection using an airbag and a seatbelt.
A conventional configuration of a passenger protection device for implementing thorough passenger protection using an airbag and a seatbelt at the time of a vehicle accident is known. For example, Japanese Unexamined Patent Application Publication No. 11-20607 discloses a passenger protection device of a configuration where a passenger detecting means for detecting whether or not a passenger is seated, the weight thereof, whether or not a child seat is present, and so forth is provided, and an airbag is controlled based on the passenger detecting means.
However, with the passenger protection device described in Japanese Unexamined Patent Application Publication No. 11-20607 (incorporated by reference herein), a combination of a weight sensor serving as passenger detecting means and a belt tension sensor for detecting the tension of the seatbelt installed to the vehicle seat are a common configuration for determining the directly seated object on the vehicle seat. With this configuration, in the event that the directly seated object is a passenger, the weight sensor is used, and on the other hand, in the event that the directly seated object is a child seat, there is a need to ensure reliable detection by also using the belt tension sensor in addition to the weight sensor, since the tightening force of the seatbelt acts upon the vehicle seat. Accordingly, with such a configuration, both a weight sensor and a belt tension sensor are necessary, and further, highly-reliable sensors and complicated circuits are necessary to suppress detection error, leading to increased costs.
Accordingly, there is a great demand for reducing device costs in the design of this type of passenger protection device by creating a mechanism capable of accurately determining the directly seated object on the vehicle seat with the conventional configuration.
The present invention has been made in light of these points, and it is an object thereof to provide an effective technique to realize a passenger protection device capable of implementing thorough passenger protection at low costs.